The importance of peri-interactions in determining the half-chair conformation of the dihydropyran ring in 2-benzopyrans. Stereochemical consequences

peri-Interactions are important in determining both the conformation of the dihydropyran ring of 2-benzopyrans as well as the stereochemistry of its substituents.     

Biologically Relevant Macrocyclic Complexes of Copper Spectral, Magnetic, Thermal and Antibacterial Approach

Copper(II) macrocyclic complexes have been synthesized with five novel ligands: L¹-1,7,10,16-tetraaza-2,6,11,15-tetraone-4,13-dithiacycloocta-decane, L²-1,7,11,17-tetraaza-2,6,12,16-tetraone-4,14-dithia-cyclocosane, L³-1,7,10, 13,19,22-hexaaza-2,6,14,18-tetraone-4,16-dithiacyclo-tetracosane, L⁴-1,7,14,20,tetraaza-2,6,15,19-tetraone-4,17,di- thiatricyclo [22, 4, O^21,26, O^8,13] hexacosa-8,10,12,21,23,25-hexene, L⁵- 1,7,13,19,25,26-hexaaza-2,6,14,18 tetraone-4,16 dithia tricyclo [23, 3, 1, I^8,12] hexacosa [8(26), 10, 12, 20(25), 22, 24] hexane and characterized by elemental analysis, molar conductance, magnetic susceptibility, i.r, u.v.–vis, EPR spectral studies, thermal studies and electrochemical properties. The molar conductance measurements of the complexes in DMSO correspond to 1:2 electrolytes. g-Values are calculated for all of the complexes in the polycrystalline form as well as in DMSO solution. On the basis of i.r, electronic and EPR spectral studies a square planar geometry has been assigned to these complexes. Cyclic voltammograms for all the complexes are similar to quasi-reversible redox processes Cu^IICu^II⇆Cu^IICu^I⇆Cu^ICu^I. The complexes were also evaluated against the growth of bacteria (S. fecalis and E.coli) in vitro. An erratum to this article is available at .     

'Double asymmetric induction' as a novel tool for high stereocontrol in Baylis-Hillman reaction

The strategy of double asymmetric induction was utilized in Baylis-Hillman reaction for the first time by the coupling of chiral aldehydes with chiral acrylate (1,2:5,6-di-O-isopropylidene-alpha-D-glucofuranose-3-acrylate) to obtain corresponding adducts with high syn diastereoselectivities (de >90%) in moderate to good yields.     

Novel copper(II) homobinuclear macrocyclic complexes: cyclic voltammetry, biological properties and spectral studies

A series of five new copper(II) macrocyclic complexes have been synthesized by template condensation. The bonding and stereochemistry of the complexes have been characterized by elemental analysis, molar conductance, magnetic susceptibility, IR, UV-visible, EPR spectral studies and electrochemical properties. g-Values are calculated for all of the complexes in polycrystalline form as well as in DMSO solution. The magnetic and spectral data indicate square planar geometry for all the complexes. Cyclic voltammograms for all the complexes are similar and involve two quasi-reversible redox processes. Cu(II)Cu(II)<=>Cu(II)Cu(I)<=>Cu(I)Cu(I). Their biological properties have also been studied. The macrocyclic complexes show more anti-bacterial than controlled one. The anti-bacterial activities of the compounds were tested against Streptococcus fecalis and Escherichia coli with different concentrations.     

EPR, UV-vis, magnetic, spectral studies and electrochemical behaviour of mononuclear transition metal complexes derived from novel hexa-aza-macrotricyclic ligand

Aza-macrocyclic complexes have gained importance because of their pharmacological properties. Hexa-aza-macrocycles containing glutarimide efficiently coordinate as hexa-dentate ligand, to give complexes of Cu(II) possessing tetragonal structure and Mn(II), Co(II) and Ni(II) metal ions that are essentially octahedral. Spectroscopic, and chemical characterizations of these systems are presented in this article. For Ni(II) complexes results on electron transfer processes measured by cyclic voltammetry and colourimetry have been studied.     

Effects of (60)Co gamma radiation on thylakoid membrane functions in Anacystis nidulans

In photosynthetic organisms oxidative stress is known to result in photoinactivation of photosynthetic machinery. We investigated effects of ⁶⁰Co γ radiation, which generates oxidative stress, on thylakoid structure and function in cyanobacteria. Cells of unicellular, non-nitrogen fixing cyanobacterium Anacystis nidulans (Synechococcus sp.) showed D₁₀ value of 257 Gy of ⁶⁰Co γ radiation. When measured immediately after exposure, cells irradiated with 1500 Gy (lethal dose) of ⁶⁰Co γ radiation did not show any differences in photosynthetic functions such as CO₂ fixation, O₂ evolution and partial reactions of photosynthetic electron transport in comparison to unirradiated cells. Incubation of irradiated cells for 24 h in light or dark resulted in decline in photosynthesis. The decline in photosynthesis was higher in the cells incubated in light as compared to the cells incubated in dark. Among the partial reactions of electron transport, only PSII activity declined drastically after incubation of irradiated samples. This was also supported by the analysis of membrane functions using thermoluminescence. Exposure of cyanobacteria to high doses of ⁶⁰Co γ radiation did not affect the thylakoid membrane ultrastructure immediately after exposure as shown by electron microscopy. The level of reactive oxygen species (ROS) in irradiated cells was 20 times higher as compared to control. In irradiated cells de novo protein synthesis was reduced considerably immediately after irradiation. Treatment of cells with tetracycline also affected photosynthesis as in irradiated cells. The results showed that photoinhibition of photosynthetic apparatus after incubation of irradiated cells was probably augmented due to reduced protein synthesis. Active photosynthesis is known to require uninterrupted replenishment of some of the proteins involved in electron transport chain. The defective thylakoid membrane biogenesis may be leading to photosynthetic decline post-irradiation.     

Development of an amperometric sulfite biosensor based on a gold nanoparticles/chitosan/multiwalled carbon nanotubes/polyaniline-modified gold electrode

A sulfite oxidase (SOx) purified from leaves of Syzygium cumini (Jamun) was immobilized covalently onto a gold nanoparticles (AuNPs)/chitosan (CHIT)/carboxylated multiwalled carbon nanotubes (cMWCNTs)/polyaniline (PANI) composite that was electrodeposited onto the surface of a gold (Au) electrode. A novel and highly sensitive sulfite biosensor was developed that used this enzyme electrode (SOx/AuNPs/CHIT/cMWCNT/PANI/Au) as the working electrode, Ag/AgCl as the standard electrode, and Pt wire as the auxiliary electrode. The modified electrode was characterized by Fourier transform infrared (FTIR) spectroscopy, cyclic voltammetry (CV), scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS) before and after the immobilization of the SOx. The sensor produced its optimum response within 3 s when operated at 50 mVs⁻¹ in 0.1 M phosphate buffer, pH 7.0, and at 35 °C. The linear range and detection limit of the sensor were 0.75–400 μM and 0.5 μM (S/N = 3), respectively. The biosensor was employed to determine sulfite levels in fruit juices and alcoholic beverages. The enzyme electrode was used 300 times over a period of three months when stored at 4 °C.     

Volumetric and ultrasonic behaviour of binary mixtures of 1-nonanol with o-cresol,m-cresol,p-cresol and anisole at T = (293.15 and 313.15) K

Densities, ρ, and speeds of sound, u, of binary liquid mixtures of 1-nonanol with o-cresol, m-cresol, p-cresol and anisole have been measured over the entire range of composition at T = (293.15 and 313.15) K and at atmospheric pressure. Using these data, the excess molar volume, V^E, molar free volume, V_f, parameters related to space-filling ability, V_f/V, non-linearity parameters, B/A, isentropic compressibility, κ_S, molar isentropic compressibility, K_S,m, deviation of molar isentropic compressibility, $K_{S\text{,}m}^E$, deviations of the speed of sound, u^D, and limiting excess partial molar volume, ${\overline{V}}_{m\text{,}i}^{E\text{,}0}$, and isentropic compressibility, ${\overline{K}}_{m\text{,}i}^{E\text{,}0}$, have been calculated. The calculated excess and deviation functions have been fitted to the Redlich–Kister polynomial equations and the results analyzed in terms of molecular interactions and structural effects.     

Regioselective synthesis of 2,3,4- or 2,3,5-trisubstituted pyrroles via [3,3] or [1,3] rearrangements of O-vinyl oximes

The regioselective synthesis of 2,3,4- or 2,3,5-trisubstituted pyrroles has been achieved via [3,3] and [1,3] sigmatropic rearrangements of O-vinyl oximes, respectively. Iridium-catalyzed isomerization of easily prepared O-allyl oximes enables rapid access to O-vinyl oximes. The regioselectivity of pyrrole formation can be controlled by either the identity of the α-substituent or through the addition of an amine base. When enolization is favored, a [3,3] rearrangement followed by a Paal-Knorr cyclization provides a 2,3,4-trisubstituted pyrrole; when enolization is disfavored, a [1,3] rearrangement occurs prior to enolization to produce a 2,3,5-trisubstituted pyrrole after cyclization. Optimization and scope of the O-allyl oxime isomerization and subsequent pyrrole formation are discussed and mechanistic pathways are proposed. Conditions are provided for selecting either the [3,3] rearrangement or the [1,3] rearrangement product with β-ester O-allyl oxime substrates.     

Ab initio study of mechanical strength of solid polymer electrolyte (PEO)5LiClO4

Mechanical strength is one of the significant properties of any solid polymer electrolyte of electrochemical devices, therefore; the ab initio study based on density functional theory is performed, and the bond strength of Poly ethylene oxide (PEO)₅ polymer without and with Lithium Perchlorate (LiClO₄) is investigated. The central oxygen atom of PEO is displaced till to respective bond is broken along X, Y, and Z directions, respectively. The same is simulated in the presence of LiClO₄ and the minimum bond breaking energy which is also called the mechanical strength is calculated along three directions. Higher energy is required in compression of (PEO)₅ along x and y axes than expansion, and vice versa along z axis. The same is observed for (PEO)₅-LiClO₄ polymer electrolyte along x and y axes, along z direction; the energy required is nearly same for compression/expansion. Due to this energy, crystalline nature of a polymer is reduced and amorphous nature is increased. In DOS analysis, the forbidden energy gap of (PEO)₅-LiClO₄ is reduced by 1.0 eV than (PEO)₅; it causes to increase the lithium cation concentration and the ionic conductivity.